We present a discussion of the design issues and trade-offs that have been considered in putting together a new concept for MOSAIC,1, 2 the multi-object spectrograph for the E-ELT. MOSAIC aims to address the combined science cases for E-ELT MOS that arose from the earlier studies of the multi-object and multi-adaptive optics instruments (see MOSAIC science requirements in [3]). MOSAIC combines the advantages of a highly-multiplexed instrument targeting single-point objects with one which has a more modest multiplex but can spatially resolve a source with high resolution (IFU). These will span across two wavebands: visible and near-infrared.

GRAVITY is a second generation near-infrared VLTI instrument that will combine the light of the four unit or four auxiliary telescopes of the ESO Paranal observatory in Chile. The major science goals are the observation of objects in close orbit around, or spiraling into the black hole in the Galactic center with unrivaled sensitivity and angular resolution as well as studies of young stellar objects and evolved stars. In order to cancel out the effect of atmospheric turbulence and to be able to see beyond dusty layers, it needs infrared wave-front sensors when operating with the unit telescopes. Therefore GRAVITY consists of the Beam Combiner Instrument (BCI) located in the VLTI laboratory and a wave-front sensor in each unit telescope Coudé room, thus aptly named Coudé Infrared Adaptive Optics (CIAO). This paper describes the CIAO design, assembly, integration and verification at the Paranal observatory.

The use of sodium laser guide star for Extremely Large Telescopes (ELT) adaptive optics systems is a key concern due to the perspective effect that produces elongated images in the Shack-Hartmann pattern. In order to assess the feasibility of using an elongated sodium beacon on an ELT, an on-sky experiment reproducing the extreme off-axis launch conditions of the European ELT is scheduled for summer and autumn 2016. The experiment will use the demonstrator CANARY installed on the William Herschel Telescope and the ESO transportable 20W CW fiber laser, embedded in the Wendelstein LGS unit. We will discuss here the challenges this experiment addresses as well as the details of its implementation and the derivation of the error budget.

MICADO is the E-ELT first-light imager, working at the diffraction limit in the near-infrared. Multi-conjugate adaptive optics (MCAO) will be the primary AO mode of MICADO, driving the design of the instrument. It will be provided by MAORY, the E-ELT first-light AO module. MICADO will also come with a SCAO capability, jointly developed by MICADO and MAORY. SCAO will be the first AO mode to be tested at the telescope, in a phased approach of AO integration at the E-ELT.

We present in the following the MICADO-MAORY SCAO specifications, the current SCAO prototyping activities at LESIA for E-ELT scale pyramid wavefront sensor (WFS) and real-time computer (RTC), our activities on end-to-end AO simulations and the current preliminary design of SCAO subsystems. We finish by presenting the implementation and current design studies for the high-contrast imaging mode of MICADO, which will make use of the SCAO correction offered to the instrument.

MOSAIC is the proposed multiple-object spectrograph for the E-ELT that will utilise the widest possible field of view provided by the telescope. In terms of adaptive optics, there are two distinct operating modes required to meet the top-level science requirements. The MOSAIC High Multiplex Mode (HMM) requires either seeing-limited or GLAO correction within a 0.6 (NIR) and 0.9 (VIS) arcsecond sub-fields over the widest possible field for a few hundred objects. To achieve seeing limited operation whilst maintaining the maximum unvignetted field of view for scientific observation will require recreating some of the functionality present in the Pre-Focal Station relating to control of the E-ELT active optics. MOSAIC High Definition Mode Control (HDM) requires a 25% Ensquared Energy (EE) within 150mas in the H-band element for approximately 10 targets distributed across the full E-ELT field, implying the use of Multiple Object AO (MOAO). Initial studies have shown that to meet the EE requirements whilst maintaining high-sky coverage will require the combination of wavefront signals from both high-order NGS and LGS to provide a tomographic estimate for the correction to be applied to the open-loop MOAO DMs. In this paper we present the current MOSAIC AO design and provide the first performance estimates for the baseline instrument design. We then report on the various trade-offs that will be investigated throughout the course of the Phase A study, such as the requirement to mix NGS and LGS signals tomographically. Finally, we discuss how these will impact the AO architecture, the MOSAIC design and ultimately the scientific performance of this wide-field workhorse instrument at the E-ELT.

CANARY is an on-sky Laser Guide Star (LGS) tomographic AO demonstrator in operation at the 4.2m William Herschel Telescope (WHT) in La Palma. From the early demonstration of open-loop tomography on a single deformable mirror using natural guide stars in 2010, CANARY has been progressively upgraded each year to reach its final goal in July 2015. It is now a two-stage system that mimics the future E-ELT: a GLAO-driven woofer based on 4 laser guide stars delivers a ground-layer compensated field to a figure sensor locked tweeter DM, that achieves the final on-axis tomographic compensation. We present the overall system, the control strategy and an overview of its on-sky performance.

We present the current optical design of the Relay Optics (RO) dedicated to the single-conjugate adaptive optics (SCAO) mode for the first light E-ELT imaging camera MICADO. MICADO is a wide-field near-IR camera featuring a 75 arcsec field of view, with spectrographic, astrometric, and coronagraphic capabilities. It has been chosen by ESO as one of the two first-light instruments. MICADO will be optimized for the multi-conjugate adaptive optics module MAORY and will also work in SCAO mode to provide a high-level, on-axis correction (making use of the adaptive secondary M4 in the telescope). For full scientific exploitation and in a phase approach for developing AO performance at the ELT, a SCAO mode is needed for MICADO. It will be a joint development between the MICADO and MAORY consortia and in the long term integrated in MAORY. Different options are presented to accommodate different set of requirements, the development plan of MICADO and MAORY instruments will lead to the final configuration and the used of the SCAO and its RO. They allow Coronagraphic observations providing an intermediate pupil plane to accommodate an atmospheric dispersion corrector and an apodizer.

CANARY is the multi-object adaptive optics (MOAO) on-sky demonstrator developed by Durham University and LESIA Observatoire de Paris, in the perspective of the E-ELT. Since 2013, CANARY has been operating with 3 off-axis NGS and 4 off-axis Rayleigh LGS and compensating for one on-axis NGS observed with a near IR camera and the Truth Sensor (TS) for diagnostic purpose. In this paper, we present the tomographic performance of CANARY during the runs in 2013. We propose a detailed analysis of the tomographic error leading to the establishment of the CANARY wave-front error budget. In particular we are able to evaluate the tomographic error for each altitude in the atmosphere for a given reconstructor by modelling a set of one-layer covariance matrices. This tool allows us to understand the tradeoffs to be made in the building of the tomographic reconstructor. We present two methods for the wavefront error budget computation. The DTI one uses input system parameters and open loop WFS slopes to estimate the error in a number of independent terms. The DMTS method directly uses the Truth Sensor measurements to estimate the error. We show a good agreement between the two approaches making us confident in our modelling of the instrument. We derive estimations of the Strehl ratio from the error variance and compare them to the recorded IR image Strehl ratio. We find a good agreement between the two, hence validating our wavefront error analysis. Finally we present an on-sky validation of the tomographic reconstruction using LGS based on GLAO and MOAO data. We also quantify the gain brought by the LGS, comparing results obtained in MOAO with 3 NGS and with or without LGS in the wavefront measurements.

We present in this paper an overview of the single-conjugate adaptive optics (SCAO) module of the wide-field imager MICADO. MICADO is a near-IR camera for the European ELT, featuring a wide field (75"), spectroscopic and coronagraphic capabilities. It has been chosen by ESO as one of the two first-light instruments. MICADO will be optimized for the multi-conjugate adaptive optics module MAORY and will also work in SCAO mode. This SCAO mode will provide MICADO with a high-level, on-axis correction, making use of the M4 adaptive mirror in the telescope. We present first the current design of the different subsystems of the SCAO module (namely the optical relay interfacing MICADO to the telescope in its SCAO mode, the wavefront sensor, the real-time computer and the high contrast imaging). We then present the adaptive optics and coronagraphic simulations. The following section is devoted to the presentation of the project organization. We end with the conclusions and perspectives of the project.

CANARY is an on-sky Laser Guide Star (LGS) tomographic AO demonstrator that has been in operation at the 4.2m William Herschel Telescope (WHT) in La Palma since 2010. In 2013, CANARY was upgraded from its initial configuration that used three off-axis Natural Guide Stars (NGS) through the inclusion of four off-axis Rayleigh LGS and associated wavefront sensing system. Here we present the system and analysis of the on-sky results obtained at the WHT between May and September 2014. Finally we present results from the final ‘Phase C’ CANARY system that aims to recreate the tomographic configuration to emulate the expected tomographic AO configuration of both the AOF at the VLT and E-ELT.

MOONS is a new Multi-Object Optical and Near-infrared Spectrograph selected by ESO as a third generation
instrument for the Very Large Telescope (VLT). The grasp of the large collecting area offered by the VLT (8.2m
diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.8μm - 1.8μm) of MOONS
will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of
Galactic, Extragalactic and Cosmological studies and provide crucial follow-up for major facilities such as Gaia,
VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over
the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of very
first galaxies and re-ionization of the Universe at redshift z>8-9, just few million years after the Big Bang. On a
timescale of 5 years of observations, MOONS will provide high quality spectra for >3M stars in our Galaxy and the
local group, and for 1-2M galaxies at z>1 (SDSS-like survey), promising to revolutionise our understanding of the
Universe.
The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol
field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8μm-1.8μm and two resolution
modes: medium resolution and high resolution. In the medium resolution mode (R~4,000-6,000) the entire wavelength
range 0.8μm-1.8μm is observed simultaneously, while the high resolution mode covers simultaneously three selected
spectral regions: one around the CaII triplet (at R~8,000) to measure radial velocities, and two regions at R~20,000 one
in the J-band and one in the H-band, for detailed measurements of chemical abundances.

In ground based astronomy, mainly all designs of sky survey telescopes are limited by the requirement
that the detecting surface is flat whereas the focal surface is curved. Two kinds of solution have been
investigated up to now. The first one consists in adding optical systems to flatten the image surface; however this
solution complicates the design and increases the system size. Somehow, this solution increases, in the same
time, the weight and price of the instrument. The second solution consists in curving artificially the focal surface
by using a mosaic of several detectors, which are positioned in a spherical shape. However, this attempt is
dedicated to low curvature and is limited by the technical difficulty to control the detectors alignment and tilt
between each others.
Today we would like to propose an ideal solution which is to curve the focal plane array in a spherical shape,
thanks to our monolithic process developed at CEA-LETI based on thinned silicon substrates which allows a
100% optical fill factor. Two infrared uncooled cameras have been performed, using 320 x 256 pixels and 25 μm
pitch micro-bolometer arrays curved at a bending radius of 80 mm. These two micro-cameras illustrate the
optical system simplification and miniaturization involved by curved focal plane arrays.
Moreover, the advantages of curved detectors on the optical performances (Point Spreading Function), as well as
on volume and cost savings have been highlighted by the simulation of the opto-mechanical architecture of the
spectrometer OptiMOS-EVE for the European Extremely Large Telescope (E-ELT).

MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large
Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of ~1000 fibers deployable over a
field of view of ~500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total
wavelength coverage is 0.8μm-1.8μm and two resolution modes: medium resolution and high resolution. In the medium
resolution mode (R~4,000-6,000) the entire wavelength range 0.8μm-1.8μm is observed simultaneously, while the high
resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R~8,000) to
measure radial velocities, and two regions at R~20,000 one in the J-band and one in the H-band, for detailed
measurements of chemical abundances.
The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of
MOONS – extending into the near-IR – will provide the observational power necessary to study galaxy formation and
evolution over the entire history of the Universe, from our Milky Way, through the redshift desert and up to the epoch
of re-ionization at z<8-9. At the same time, the high spectral resolution mode will allow astronomers to study chemical
abundances of stars in our Galaxy, in particular in the highly obscured regions of the Bulge, and provide the necessary
follow-up of the Gaia mission. Such characteristics and versatility make MOONS the long-awaited workhorse near-IR
MOS for the VLT, which will perfectly complement optical spectroscopy performed by FLAMES and VIMOS.

The EAGLE and EVE Phase A studies for instruments for the European Extremely Large Telescope (E-ELT) originated
from related top-level scientific questions, but employed different (yet complementary) methods to deliver the required
observations. We re-examine the motivations for a multi-object spectrograph (MOS) on the E-ELT and present a unified
set of requirements for a versatile instrument. Such a MOS would exploit the excellent spatial resolution in the near-infrared envisaged for EAGLE, combined with aspects of the spectral coverage and large multiplex of EVE. We briefly
discuss the top-level systems which could satisfy these requirements in a single instrument at one of the Nasmyth foci of
the E-ELT.

Context. To characterize their atmospheres in order to find evidences of life, one has to detect directly
photons from the exoplanets to measure their spectra. One possible technique is dark fringe
interferometry that needs an achromatic π phase shift in one arm of the interferometer. We have
conceived a phase shifter made of two cellular mirrors, in which each cell position and phase shift is
specific, so that the behaviour of the nulling with respect to wavelength is flat within a broad range.
Aims. We want to validate experimentally two versions of this achromatic phase shifter: a transmissive
one in bulk optics and a reflective one using a segmented deformable mirror. What we present in this
paper are the last results obtained in the lab.
Methods. We built an optical bench in the visible that allows us to test the principle and characterize
the performances and the limits of this phase shifter.
Results. We tested several transmissive and one reflective phase shifter and obtained, for instance, an
attenuation of about 2.10-3 for a white source (from 430 to 830 nm) that proved the achromatic
behavior of the phase shifter. The preliminary performances and limitations are analyzed.

CANARY is an on-sky demonstrator adaptive optics (AO) system that in 2010 provided the first on-sky demonstration
of open-loop tomographic adaptive optics correction using natural guide stars (NGS). Phase B of the CANARY
experiment aims to extend the instrument from its original configuration by also measuring wavefronts from four offaxis
Rayleigh laser guide stars (LGS). This upgrade allows CANARY to perform tomographic wavefront sensing over a
2.5arcminute field of view using any mix of up to seven off-axis wavefront sensors (four LGS and three NGS)
simultaneously. AO correction within CANARY is performed on-axis along a single line of sight using a 52-actuator
deformable mirror being controlled in open-loop. Here we give an overview of the Phase B LGS system, discuss the
calibration of a mixed NGS/LGS tomographic system and present the recent laboratory and on-sky results from the
Phase B commissioning.

The OPTIMOS-EVE concept provides optical to near-infrared (370-1700 nm) spectroscopy, with three spectral
resolution (5000, 15000 and 30000), with high simultaneous multiplex (at least 200). The optical fibre links are
distributed in four kinds of bundles: several hundreds of mono-object systems with three types of bundles, fibre size
being used to adapt spectral resolution and 30 deployable medium IFUs (about 2"x3"). We are optimising the design of
deployable IFUs to warrant sky subtraction for the faintest extragalactic sources.
This paper gives the design and results of the prototype for the high resolution mode and the preliminary design of a
medium IFU developed in collaboration between the GEPI and the LNA.

The CANARY on-sky MOAO demonstrator is being integrated in the laboratory and a status update about its
various components is presented here. We also discuss the alignment and calibration procedures used to improve
system performance and overall stability. CANARY will be commissioned at the William Herschel Telescope at
the end of September 2010.

Context. Dark fringe interferometry in the thermal infrared is one way to detect directly a planet orbiting a star, and so to
characterize the planet's atmosphere through spectroscopy. This method demands a phase shift of π1 in one arm of the
interferometer. In order to detect various bio-tracers gases, a broad wavelength range (6-18 μm)2-3 is necessary, therefore
an achromatic phase shift of π is required. The achromatic device presented here is a phase shifter made of two cellular
mirrors, in which each cell induces a specific phase shift.
Aims. We wish to demonstrate that this theoretical concept is experimentally valid. We present in this paper the setup
and the very first results.
Methods. In a first step, we have consolidated the theoretical ground and in a second step we developed an optical bench
in the visible domain to test the concept and measure the performances of this device.
Results. The preliminary experimental tests show evidences that such a device is working as expected in terms of nulling
and achromatism: in spite of an error on one cell of the prototype, it provides a nulling of 2.10-3 at one wavelength, and
this value is close to the expected value. Besides, a nulling of 1.10-2 in a 450 to 750 nm bandwidth: a hint that a perfect
device should be achromatic.

OPTIMOS-EVE (OPTical Infrared Multi Object Spectrograph - Extreme Visual Explorer) is the fiber fed multi object
spectrograph proposed for the E-ELT. It is designed to provide a spectral resolution ranging from 5000 to 30.000, at
wavelengths from 0.37 μm to 1.70 μm, combined with a high multiplex (>200) and a large spectral coverage. The
system consists of three main modules: a fiber positioning system, fibers and a spectrograph.
The OPTIMOS-EVE Phase-A study, carried out within the framework of the ESO E-ELT instrumentation studies, has
been performed by an international consortium consisting of institutes from France, Netherlands, United Kingdom, Italy
and Denmark.
This paper describes the design tradeoff study and the key issues determining the price and performance of the
instrument.

OPTIMOS-EVE is a fiber-fed, high-multiplex, high-efficiency, large spectral coverage spectrograph for EELT covering
visible and near-infrared simultaneously. More than 200 seeing-limited objects will be observed at the same time over
the full 7 arcmin field of view of the telescope, feeding the spectrograph, asking for very large multiplexing at the
spectrograph side. The spectrograph consists of two identical units. Each unit will have two optimized channels to
observe both visible and near-infrared wavelengths at the same time, covering from 0.37 to 1.7 micron. To maximize the
scientific return, a large simultaneous spectral coverage per exposure was required, up to 1/3 of the central wavelength.
Moreover, different spectral resolution modes, spanning from 5'000 to 30'000, were defined to match very different sky
targets. Many different optical solutions were generated during the initial study phase in order to select that one that will
maximize performances within given constraints (mass, space, cost). Here we present the results of this study, with
special attention to the baseline design. Efforts were done to keep size of the optical components well within present
state-of-the-art technologies. For example, large glass blank sizes were limited to ~35 cm maximum diameter. VPH
gratings were selected as dispersers, to improve efficiency, following their superblaze curve. This led to scanning
gratings and cameras. Optical design will be described, together with expected performances.

The OPTIMOS-EVE concept provides optical to near-infrared (370-1700 nm) spectroscopy, with three spectral
resolution (5000, 15000 and 30000), with high simultaneous multiplex (at least 200). The optical fibre links are
distributed in five kinds of bundles: several hundreds of mono-object systems with three types of bundles, fibre size
being used to adapt slit with, and thus spectral resolution, 30 deployable medium IFUs (about 2"×3") and one large IFU
(about 6"×12").
This paper gives an overview of the design of each mode and describes the specific developments required to optimise
the performances of the fibre system.

OPTIMOS-EVE (OPTical Infrared Multi Object Spectrograph - Extreme Visual Explorer) is the fibre fed multi object
spectrograph proposed for the European Extremely Large Telescope (E-ELT), planned to be operational in 2018 at Cerro
Armazones (Chile). It is designed to provide a spectral resolution of 6000, 18000 or 30000, at wavelengths from 370 nm
to 1.7 μm, combined with a high multiplex (>200) and a large spectral coverage. Additionally medium and large IFUs
are available. The system consists of three main modules: a fibre positioning system, fibres and a spectrograph.
The recently finished OPTIMOS-EVE Phase-A study, carried out within the framework of the ESO E-ELT
instrumentation studies, has been performed by an international consortium consisting of institutes from France,
Netherlands, United Kingdom and Italy. All three main science themes of the E-ELT are covered by this instrument:
Planets and Stars; Stars and Galaxies; Galaxies and Cosmology.
This paper gives an overview of the OPTIMOS-EVE project, describing the science cases, top level requirements, the
overall technical concept and the project management approach. It includes a description of the consortium, highlights of
the science drivers and resulting science requirements, an overview of the instrument design and telescope interfaces, the
operational concept, expected performance, work breakdown and management structure for the construction of the
instrument, cost and schedule.

EAGLE is a wide FoV (5 arcmin diameter), multi-objects (at least 20) integral-field spectrograph (R>4000) for the E-ELT.
The top level requirements are to concentrate 30 to 40 % of the photons collected by the E-ELT in a focal area of
75x75 mas2 in H band. This leads to the selection of the Multi Object Adaptive Optics in order to deliver such a
performance in a so-large FoV. In this paper, we present a detailed analysis of the error budget for an MOAO system in
EAGLE. It is based on numerical simulation results. The budget is splitted in LGS and NGS contributions. The analysis
leads to share the specifications between low spatial frequencies and high spatial frequencies in the wave-front errors.
Finally a preliminary conceptual design of the MOAO system is deduced including 9 LGS for tomography and a 9000
actuator deformable mirror per channel.

We recently presented a new concept for designing an achromatic phase shifter. An APS is required in nulling interferometry,
a technique that aims at directly detecting and characterizing planets around a star in the thermal infrared. Our solution
is based on two cellular mirrors (alternatively, transparent plates can be used) where cells have thickness which introduce
OPD that are respectively odd and even multiples of half the central wavelength, on the fraction of the wave it reflects. A
destructive interference is thus produced on axis for the central wavelength when recombining the two beams. We have
shown that if the thicknesses are distributed according to the Pascal triangle, a fair quasi-achromatism is also reached on
typically one octave in wavelength, provided there is a suffcient number of cells. The major interest of this solution is
that it allows a compact, simple and fully symmetric design, without complex sub-systems to adjust. In this paper, after
reminding the basic concept, we first present the theoretical estimations for the expected performances in the two possible
regimes of recombination: on axis and multi-axial (Fizeau). We then describe the laboratory setup of the demonstration
bench we are developing, as well as the first results obtained.

EAGLE is a multi-object 3D spectroscopy instrument currently under design for the 42-metre European Extremely Large
Telescope (E-ELT). Precise requirements are still being developed, but it is clear that EAGLE will require (~100 x 100
actuator) adaptive optics correction of ~20 - 60 spectroscopic subfields distributed across a ~5 arcminute diameter field
of view. It is very likely that LGS will be required to provide wavefront sensing with the necessary sky coverage. Two
alternative adaptive optics implementations are being considered, one of which is Multi-Object Adaptive Optics
(MOAO). In this scheme, wavefront tomography is performed using a set of LGS and NGS in either a completely open-loop
manner, or in a configuration that is only closed-loop with respect to only one DM, probably the adaptive M4 of the
E-ELT. The fine wavefront correction required for each subfield is then applied in a completely open-loop fashion by
independent DMs within each separate optical relay. The novelty of this scheme is such that on-sky demonstration is
required prior to final construction of an E-ELT instrument. The CANARY project will implement a single channel of an
MOAO system on the 4.2m William Herschel Telescope. This will be a comprehensive demonstration, which will be
phased to include pure NGS, low-order NGS-LGS and high-order woofer-tweeter NGS-LGS configurations. The LGSs
used for these demonstrations will be Rayleigh systems, where the variable range-gate height and extension can be used
to simulate many of the LGS effects on the E-ELT. We describe the requirements for the various phases of MOAO
demonstration, the corresponding CANARY configurations and capabilities and the current conceptual designs of the
various subsystems.

E-ELT will provide a unique opportunity to observe the early universe since its large collecting area will allow detecting
faint objects at high redshifts. Primordial galaxies are a key topic for cosmology and for understanding the behaviour of
the galaxies in the universe. To achieve these observations, future instruments for the E-ELT will have to provide high
sensitivity over a wide range of wavelengths from 1 μm up to 2.5 μm - the upper limit being imposed by the redshift
which shifts the OII and Hα lines.
For the EAGLE instrument mainly devoted to such observations, we have studied the opto-thermal behaviour of the
complete system (TAS - Target Acquisition System - and the spectrograph) to estimate the thermal emission of the
optical and the mechanical parts which become a major contributor to the background above 2.2 μm. The nominal
operating temperature is a key parameter we must define precisely to both reduce the thermal background and optimise
the cooling system in terms of cost and complexity. The results of the simulations show that the TAS and the
spectrograph contribute to the thermal background at a similar level and what the optimal temperature should be. We
then discuss how such an 'optimal design' might be implemented in practice.

This paper summarizes the different optical concepts developed for the EAGLE Phase A design. EAGLE will be an
MOAO (Multi-object AO) IFU spectrometer operating between 0.8 and 2.5μm. The EAGLE consortium have
developed different concepts for the challenging problem of acquiring more than twenty objects in the patrol field of
view (FOV), correcting the wavefront along the line of sight to each of the objects and analyzing each object spatially
and spectrally with an Integral Field Spectrograph. The target selection FOV will be ≥20 square arcmin and the
individual target FOV can be selected to be either 1.65×1.65arcsec or 1.65×3.3arcsec. They will be sampled spatially at
75mas and with spectral resolutions of 4000 and 10000. Optical designs for target acquisition systems, integral-field
unit, and spectrographs have been developed. These will be compared and the expected performance will be described
in terms of the number of targets, overall patrol field of view, individual field of view, throughput, spectral resolving
power and image quality.

EAGLE is an instrument under conceptual study for the European Extremely Large Telescope (E-ELT). EAGLE will be
installed at the Gravity Invariant Focal Station of the E-ELT, covering a field of view between 5 and 10 arcminutes. Its
main scientific drivers are the physics and evolution of high-redshift galaxies, the detection and characterization of first-light
objects and the physics of galaxy evolution from stellar archaeology. The top level requirements of the instrument
call for 20 spectroscopic channels in the near infrared, assisted by Adaptive Optics. Several concepts of the Target
Acquisition sub-system have been studied and are briefly presented. Multi-Conjugate Adaptive Optics (MCAO) over a
segmented 5' field has been evaluated and compared to Multi-Object Adaptive Optics (MOAO). The latter has higher
performance and is easier to implement, and is therefore chosen as the baseline for EAGLE. The paper provides a status
report of the conceptual study, and indicates how the future steps will address the instrument development plan due to be
completed within a year.

Direct detection and characterization of a planet around a star by nulling interferometry, must be efficient in a large wavelength
domain in order to detect simultaneously the infrared bio-tracers CO2, O3 and H2O. This condition requires that an achromatic phase shift of π be implemented, with an accuracy sufficient for achieving a deep nulling at all considered
wavelengths. Several solutions have been presented. We present here a new concept for designing such an achromatic
phase shifter. It is based on two cellular mirrors (alternatively, transparent plates can be used) where cells have thickness
which are respectively odd and even multiples of a quarter of the central wavelength. Each cell introduces then a phase shift
of (2k + 1)π or of 2kπ, on the fraction of the wave it reflects. Each mirror is introduced in the collimated beam issued from
one or the other telescopes. Because of the odd/even distribution, a destructive interference is obviously produced on axis
for the central wavelength when recombining the two beams. The trick to obtain a quasi-achromatisation is to distribute
the thickness of the cells, so that the nulling is also efficient for a wavelength not too far from the central wavelength.
We show that if the thicknesses are distributed according to the Pascal triangle, a fair quasi-achromatism is reached. This
effect is the more efficient that the number of cells is large. For instance, with 256 × 256 cells, where phase shift range is
between -6π and +6π one shows that the nulling reaches 10-6 on the wavelength range [0.7λ0, 1.3λ0] which corresponds roughly to the DARWIN specification. In a second step, we study the optimum way to distribute the cells in the plane of the
pupil. The most important criterion is the isolation of the planet image from the residual image of the star. Several efficient
configurations are presented. Finally we consider some practical aspects on a device belonging to the real world and on the
bench we are developing. The major interest of this solution is that it allows a compact, simple and fully symmetric design,
with essentially no ajustable sub-systems ; extension to multi-telescopes interferometers with phase shift other than π can
also be envisioned.

X-shooter is a new high-efficiency integral field spectrograph mainly dedicated to the spectroscopic follow up of the gamma ray bursts. X-shooter will operate at the Cassegrain focus of the VLT with an intermediate spectral resolution of ~5000, and will provide a very wide simultaneous spectral coverage, ranging from 320 to 2500 nm. The instrument consists in a central structure which supports three prism cross-dispersed echelle spectrographs respectively optimized for the UV-blue, Visible and Near-IR wavelength ranges.
X-shooter will offer an image slicer based Integral Field Unit (IFU) designed to analyse a 1.8"x4" input field into 3 slices of 0.6"x4"and to align then on a 12" long slit. The principle of the IFU is that the central slice does not include any dioptre, the light is directly transmitted to the spectrographs. Only the two lateral sliced fields are reflected toward the two pairs of spherical mirrors and re-aligned at both ends of the previous slice in order to form the exit slit. We present here the IFU design developed at the Observatoire de Paris.

FALCON is an original concept for next generation instrumentation at ESO VLT or at future ELTs. It is a multi-objects integral field spectrograph with multiple integral field units (IFU) performing adaptive optics correction in order to reach spatial and spectral resolution ideally suited for distant galaxy studies. The resolutions required for the VLT are typically 0.15 - 0.25 arcsec and R>=5000 in the 0.8-1.8 μm wavelength range. The studied galaxies are very faint objects that cannot be directly used to perform wavefront sensing. Thus, we use at least three Wave-Front Sensors (WFS) per IFU to sense the wavefront of stars located around the galaxy, and the on-axis wavefront from the galaxy will be deduced from the off-axis measurements by atmospheric tomography, and then corrected thanks to an adaptive optics (AO) system within each IFU. Since the WFS is ideally located directly in the focal plane of the telescope, this implies to develop miniaturized devices for the wavefront sensing. Our approach is based on a Shack Hartmann principle and - instead of using a bulky detector behind - we plan to use a miniaturized system including fibers able to transport the light from the focal plane of the microlens array towards a place where the bulk issue is less critical. We draw up the main specifications of this miniaturized system and we present the characteristics of elements manufactured by using new microlithography techniques.

FALCON is an original concept for a next generation instrument which could be used on the ESO Very Large Telescope (VLT) and on the future Extremely Large Telescopes (ELT). It is a multi-objects integral field spectrograph with multiple small integral field units (IFUs). Each of them integrates a tiny adaptive optics system coupled with atmospheric tomography to solve the sky coverage problem. This therefore allows to reach spatial (0.15 - 0.25 arcsec) and spectral (R>=5000) resolutions suitable for distant galaxy studies in the 0.8-1.8 μm wavelength range. In the FALCON concept, the adaptive optics correction is only applied on small and discrete areas selected within a large field. This approach implies to develop miniaturized devices for wavefront correction such as deformable mirrors (DM) and wavefront sensors (WFS). We draw up here the main high level specifications for this instrument, that we derive in a first set of opto-mechanical DM requirements including the state of the art of DM technologies.

We present a laboratory demonstration of open loop Off-Axis Adaptive Optics with optimal control. The control based on a Minimum Mean Square Error Estimator brings a noticeable performance improvement. The next step will be to close the Off-Axis Adaptive Optics loop with a Kalman based optimal control. While this last experiment is currently under progress, a classic Adaptive Optics loop has already been closed recently with a Kalman based control and experimental results are presented. We also describe the expectable performance of the Kalman based off-axis closed loop thanks to an end-to-end simulator. Last minute notice: the Kalman based Off-Axis Adaptive Optics loop has been closed and very first results are given.

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Journal of Applied Remote SensingJournal of Astronomical Telescopes Instruments and SystemsJournal of Biomedical OpticsJournal of Electronic ImagingJournal of Medical ImagingJournal of Micro/Nanolithography, MEMS, and MOEMSJournal of NanophotonicsJournal of Photonics for EnergyNeurophotonicsOptical EngineeringSPIE Reviews